A clamping system for connecting together a first tube and a second tube, the facing ends of the tubes having bearing surfaces that project relative to the cylindrical outside surfaces of said tubes, the system comprising a collar and a washer, the collar having a band suitable for co-operating with said bearing surfaces via its inside periphery defining a setback into which the bearing surfaces can be inserted, and means for tightening said band, the washer being secured to the collar by fastening means, the system further comprising first pre-fitting means for acting when the collar is in the non-tightened state to secure said collar to the first tube when the bearing surface of said first tube is engaged in the setback.
A clamping system of this type is known from European Patent No. EP 1 451 498. The cross-section of the band of the collar is, for example, substantially V-shaped or U-shaped, so that the flanges formed by the cross-sectional shape bear respectively against the bearing surface of the first tube and against the bearing surface of the second tube. Thus, tightening the collar tends to hold the tubes clamped one against the other. A V-shaped cross-section is advantageous insofar as, when the collar is tightened, it urges the tubes together.
For example, the means for tightening the band comprise a nut-and-bolt system. Thus, the ends of the band can be turned out so as to form bearing tabs provided with holes through which a bolt can be inserted. A nut is disposed behind one of the tabs so that turning the bolt causes the collar to be tightened. However, other tightening means may be provided, e.g. of the type operating by hooking, and in particular of the type comprising a hook that is turned out relative to the band and a lug also turned out relative to the band, the hook hooking behind the lug to maintain the collar in the tightened state.
The washer of the clamping system may, in particular, serve to seal the interconnection between the two tubes, by having, for this purpose, a sealing portion that, when the system is tightened onto the tubes, is sandwiched between two sealing surfaces belonging respectively to the first tube and to the second tube.
In EP 1 451 498, the washer is secured to the collar by means of the fastening tabs with which that washer is provided, and the entire clamping system can be held pre-fitted to the first tube, by means of the pre-fitting tabs with which the washer is provided. Thus, in order to assemble the two tubes together, it is possible to pre-fit the clamping system onto the first tube and to bring the second tube closer to the first tube, before tightening the collar. In EP 1 451 498, this possibility of pre-fitting the clamping system onto the first tube constitutes a significant advantage over the pre-existing prior art in that it simplifies assembling the tubes together and connecting them together by tightening the collar.
However, that assembly operation firstly requires the second tube to be held in position relative to the assembly made up of the first tube and of the clamping system as pre-fitted on said first tube, and secondly requires the collar to be tightened by performing the appropriate manipulation. In practical terms, when assembly is performed by hand, the operator must, firstly, hold the second tube in position with one hand, and secondly perform the tightening with the other hand. The operator must therefore synchronize these movements exactly and, if tightening is not readily achievable, said operator cannot let go of the second tube to complete the tightening properly.